1. Field of the Invention
The present invention relates to transformers and, more particularly, to a cap for a transformer bushing for isolating the energized end of the same from air borne contaminants.
2. Description of the Related Art
High power electrical transformers are conventionally enclosed within a hermitically sealed, grounded metallic tank. Bushings are inserted through the top of the casing and sealed to the top of the insulating casing. One or more such bushings, either high voltage or low voltage, are installed as necessary to make the desired electrical connections to the high and low voltage windings of the coil assemblies of the transformer. The bushings provide a conductive path for the current through an opening in the metallic container of the transformer which is itself properly sealed to prevent entry therein of the moisture, gases, or dust particles. Thus, the insulating material, for example rigid porcelain, surrounds the electrical conductor. This provides the electrical conductor with lateral support and protects against electrical contact with other conductive elements such as the metallic tank. The energized end, spaced from the metallic tank, is then coupled to a cable or other conductor.
It has been found that the foregoing structure is disadvantageous in that the energized end of the porcelain bushing is not isolated from airborne contaminants and particularly salt spray where the transformer is disposed along the coast and exposed to salt water entrained in coastal breezes. When conductive salt spray contaminants in the air land on the porcelain bushing, they ultimately form a conductive surface which causes phase to ground faults resulting in power outages. Similar problems are encountered with the porcelain bushings of lighting arrestors.
It would, therefore, be desirable to provide a means for protecting the porcelain bushing from salt spray and like contaminants in the air and thus prevent the creation of a conductive surface on the porcelain.